The timestamp is correct just the human-readable time interval is slightly misleading. I notice that, for example, 8 days but "updated 2w ago" is shown instead of "updated 1w ago". 15 days, likewise, "updated 3w ago" is shown where in fact the post is updated only 2 weeks ago.
This is a small issue but sometimes it makes me think "did I post that such a long time ago".